Design of a gain-boosted telescopic fully differential amplifier with CMFB circuit

Based on Chartered 0.18μ 1.8V 1P5M CMOS process, a gain-boosted telescopic fully differential amplifier with CMFB circuit is designed and used in the sampling and holding circuit of a 14-bit, pipelined A/D converter which is supplied by 1.8 V power. In order to meet specifications, gain-boosting technique is used to improve the gain of OTA and common-mode feedback circuit is elaborately designed. Two-stages CMFB have a stable transient output of 710mV and 1V, respectively. At last, simulation results showed that 106dB loop gain, 1.13GHz unity-gain bandwidth and a phase margin of 71.75° have been achieved for the specifications of S/H circuit. The designed circuit has been applied to the front end of a 14-bit, 100MS/s pipelined ADC.